Note: Descriptions are shown in the official language in which they were submitted.
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WORK EQUALIZER AND LOADING FOR A
SINGLE ELEMENT PRINTER SELECTION SYSTEM
Background of the Invention
This invention relates to the control of the type element
of a single element typewriter.
U.S. Patent 4,094, 397 to Hughes and commonly assigned
herewith illustrates a shuttle and slider blocks useful in
controlling and defining the amount of rotation of a type-
head or type element on a single element typewriter, such
as disclosed in U.S. Patent 3,983,984 to deKler, and
similarly commonly assigned herewith.
U.S. Patent 4,094,397 discloses an improvement to the system
of U.S. Patent 3,983,984 in the replacement of the slider
blocks 18 contained in the deKler patent.
Objects of the Invention
In its broad, general aspects, the present invention
provides a selection system for a single print element
printer comprising a print element, rack and pinion means
for rotating the print element, linkage means for moving the
rack with respect to the pinion, a movement multiplier arm
having two ends, and connected to the linkage means at one
end thereof, the multiplier arm having at the opposite end
thereof a grounded pivot and connected at a point inter-
mediate the ends to a controlled displaceable member,
powered means for effecting reciprocal movement of the
controlled displaceable member, at least a stop member,
first spring bias means urging the displaceable member into
engagement with the stop member, the improvement comprising
a second bias means urgingly engaged with the rack in the
same direction of movement as the displaceable member is
spring biased by the first spring bias means, whereby the
second bias means increases the engagement force between the
controlled displaceable member and the stop member without
increasing required power of the powered means during any
portion of the cycle, above the highest level of power
provided to the power means, without the improvement.
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It is an object of the invention to increase the forces
between the slider block of the selection control
system and the rotate defining stop members without
increasing peak motor loading.
It is another object of the invention to reduce the
amount of undesired movement of the typehead to
improve locational predictability of the typehead.
The objects of the invention are accomplished by the
improvement of the invention described Xerein.
In the selection system of the type described in U.S.
Patent 4,0g4,397, a shuttle and slider blocks are
spring forced against stops which define the extent
of movement of the slider blocks which, in turn, define
the rotational movement of the typehead of the typewriter.
In order to increase the force with which the slider
block engages the stops, it is necessary to increase
the spring bias forces against the slider block which,
in turn, will be transmitted to the stops. This may
be accomplished by adding a tension spring between the
typewriter frame and the rack of the rack and pinion
portion of the selection system found in the print
rocker and more completely described in U.S. Patent
3,983,984. By adding the spring between the frame of
the typewriter and the rack, rather than increasing the
spring force between the slider block and the shuttle,
forces exerted by the added spring are utilizable for the
desired result of
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increasing the engagement force between the slider block
and the stop members whiIe not increasing the peak load
on the selection drive motor and thereby not necessitating
the increase in the motor size. This is accomplished by
virtue of the fact that the drive motor is storing
energy in or doing work on only one Qf the two springs
at any one time during the typical machine cycle and,
thus, utilizes a period during the machine cycle which
is otherwise wasted insofar as drive motor capacity is
concerned. The tension spring can be replaced by a
compression spring acting on the opposite end of the
rack positioned between the rack and the typewriter
frame although the tension spring is easier to work
with. The inclusion of this improvement spring acts
to increase the reliability of the selection system
inasmuch as it constantly bia~es the entire system in
one direction to eliminate accumulated tolerances and
thereby reduce the headplay of the type element. By
reducing the play of the type element, the detenting
of the type element prior to printing is more easily
accomplished and much more reliable.
A better understanding of the invention may be had by
referring to the drawing and detailed description to
follow.
Brief Description of the Drawings
FIG. 1 illustrates the shuttle and slider block
arrangement disclosed in U. S. Patent 4,094,397, with
the improvement added thereto.
FIG. 2 illustrates a compressive spring force exerted
on the rack in lieu of the tension spring force found
in FIG. 1.
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Detailed Description of the-Invention
.~:
Insofar as possible, the reference numerals of the
incorporated patents are used for the same parts in
this disclosure where shown and duplication is avoided.
Referring to FIG. 1, motor driven shaft 10 is driven by
motor 8 rotationally. The rotation of shaft 10 will
cause the oscillation of shuttle 100 axially along shaft
10 in response to the rotation of shaft 10. The
interaction of shaft 10 and particularly groove 116
10 illustrated in Patent 4,094,397 in FIG. 2 acting
against pin 126 on a part of shuttle 100, likewise
illustrated in FIG. 2 of 4,094,397 causes the movement
of the shuttle along shaft 10. As slider block 118
translates with shuttle 100 and stop surface 122
thereon engages one of the stop members 34 as shown
in FIG. 1 of U. S. Patent 3,983,984, slider block 118
will stop and further movement of the shuttle 100 is
accommodated by springs 108. Springs 108 provide a
biasing force to insure that stop surface 122 remains
against the stop member 54. A more detailed under-
standing of this operation may be had by a thorough
review of U. S. Patents 4,094,397 and 3,983,984.
As slider block 118 translates axially along the axis of
shaft 10, movement multiplier arm 30 attached to the
block 118 will pivot with respect to grounding point
31. Grounding point 31 is part of the typewriter
frame 27. As movement multiplier arm 30 translates in
response to the movement of slider block 118, the
displacement of the outer end thereof 29 will be in
proportion to the respective lever arm lengths. End
29 of movement multiplier arm 30 is attached to link
54 to transmit motion from arm 30 to rack 56 located
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in and supported by the rocker 68 as shown in U. S.
Patent 3,983,984. Rack`56 is provided with two sets
of gear teeth in the form of oppositely arranged racks.
Pinion 57 is engageable with one of the racks forming
rack 56 and is coupled as illustrated in FIG. 1 of
U. S. Patent 3,983,984 to type element 60.
Attached to rack 56 and urging rack 56 down and to the
right in FIG. 1 is a tension spring 90. Tenslon spring
90 acts to urge rack 56 toward frame member 27 to
which the opposite end of tension spring 90 is attached.
This urging will act to accumulate all the play in the
system such that manufacturing and assembly tolerances
will be biased and eliminated and that type element 60
will be consistently positioned for each and every
position of slider block 118;~^
An alternative embodiment is illustrated in FIG. 2
wherein a spring arrangement similar to the springs
108 are used as a compressive biasing force between
the frame of the rocker 68 and the rack 56. The
compressive force 92 may be made substantially equivalent
to the tension force exerted by spring 90 in FIG. 1
inasmuch as both tend to urge rack 56 in the identical
direction which is the same direction as the spring
biasing forces on slider block 118.
25 As the shaft 10 rotates and shuttle 100 oscillates
initially toward the right as a result of the rotation
of shaft 10 and the interaction between groove 116 and
pin 126 as shown in FIG. 2 of U. S. Patent 4,094,397,
the springs 108 will maintain slider block 118 against
30 the end of shuttle 100 until such time as surface 122
will come in contact with stop members 34 or stop 20
as shown in FIGS. 1 and 3 of U. S. Patent 3,983,984.
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At the point that surface-122 engages a resistance
force, spring 108 wll~ begin to collapse maintaining
a substantially uniform force against the stop. During
the movement described immediately above, tension spring
90 will be collapsing as movement multiplier arm also
moves with slider block 118 until such time as slider
block 118 is stopped. The remaining tension in spring
90 will add to the force urging block 118 along shaft
10 and will effectively assist springs 108 in maintaining
slider block 118 against the end of shuttle 100. Upon
engagement of surface 122 with the stop member 20, 34
of U. S. Patent 3,983,984 and the stopping of slider
block 118 from further translation, the force exerted
by spring 90 through rack 56 and link 54 will be additive
to that exerted by 108 and being transmitted to block
118. This effectively raises~-the engagement force
between surface 122 and any stop member 20, 34 engaged
thereby. As spring 108 is being collapsed by further
rotation of shaft 10 and the further shifting of
shuttle 100/ spring 90 is in a condition of stability
and equilibrium and is not affected by drive motor 8.
Energy is only being stored at this point of the cycle
in spring 108.
As the shaft continues to rotate, slider block 118 will
be engaged by shuttle 100 on its return throw and as
shuttle 100 moves leftward as seen in FIG. 1 with
respect to slider block 118, spring 108 will give up
energy previously stored therein. This force assists
in the reverse movement of shuttle 100. Upon the
restoration of slider block 118 against the end of
shuttle 100, further movement of shuttle 100 will
effect the movement of multiplier arm 30 in a clockwise
direction as viewed in FIG. 1, thus pushing on link 54
and rack 56 to return pinion 57 and type element 60 to
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the home position normally occupied during times when
no selection is occurring.
,
As this movement of rack 56 occurs in response to the
pushing by link 54, tension spring 90 is extended and
energy stored therein. As can be seen from the above,
energy is stored in tension spring 90 only after the slider
block 118 has been returned to abutting engagement
with the end of shuttle lO0 and there is no work being
performed on spring 108.
Conversely, spring 108 is only being worked on during
the portion of the cycle after surface 122 engages a
restraining force and spring 108 is being collapsed
thereafter by further movement of shuttle lO0. Inasmuch
as the stopping of slider 1l8Salso stops rack 56, at
that point there is not further movement with respect
to spring 90. Inasmuch as spring 90 is not being
deformed or allowed to deform, there is no work input
or output from spring 90 during the period of time when
work is being performed on spring 108.
This arrangement allows motor 8 to drive shaft 10 and
only perform work on spring 90 or spring 108 but not
to allow work to be performed on both sets of spring
biasing means 90, 108 at the same time. Inasmuch as
there is substantial portion of the cycle during which
spring 108 is not having energy stored in it by the
rotation of shaft lO, this allows work to be performed
by motor 8 without increasing the peak loads on motor
8 and thereby requiring an increase in the motor size
or drive capability.
Referring to FIG. 2, an alternative embodiment involves
the use of a spring 92 equivalent to that of spring 108
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in structure and characteristics. The spring may be
attached between the rocker frame 68 and rack 56 to
provide a compressive force agalnst rack 56 which, in
turn, will act through link 54. The functional result
is the same as the embodiment involving the tension
spring as illustrated in FIG. 1.
The loading or work performed on spring 92 will be done
during that portion of the cycle when the shuttle is
returning to its home position and not during a time
when the spring 108 is being compressed or flexed.
Thus, regardless of whether tension spring 90 or flex
spring 92 are utilized as illustrated, the loading of
these respective springs 90, 92 occurs during a portion
of the cycle during which no work is being performed on
spring 108 and, thus, does not increase peak load on
drive motor 8.
Having described the invention in two embodiments, it
~ is understood that minor variations may be made in the
- invention without departing from the spirit of the
invention and from the following claims.
We claim:
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